Your loved one is being held in pre-trial detention in a criminal case in Vietnam while you are abroad, and the most haunting question is often not "guilty or not" but "when will it end". In a case with foreign elements, the investigation period is not a fixed number: it can pause and then resume, running far longer than an ordinary case, and every month that passes is another month your family spends in uncertainty.
How long will the case drag on, and why does a case with foreign elements take longer than a domestic one? When the investigating authority has to request mutual legal assistance from abroad to gather evidence, will your loved one be held in detention for an extended period while waiting for the results? And if the time limit expires while the evidence from abroad has still not arrived, what happens to the case? These are very real concerns for families far away, who often receive only the bare news that someone has "been arrested" and then lose contact. This article analyses how Vietnamese law calculates the investigation period, why foreign elements lengthen a case, and the key changes taking effect in 2026 that families need to understand so as not to misread the situation.
The basic investigation period: the law counts by offence category, not by nationality
First, a distinction is needed: the "investigation period" is the time from when the competent authority issues a decision to initiate the case until the investigation concludes. Vietnamese law does not set this period according to whether the person involved is Vietnamese or foreign, but according to the seriousness of the offence charged.
What does this mean for you? The figures of 2, 3 and 4 months above are only the initial term. When a case is complex, the investigating authority may ask the Procuracy to extend the investigation, and this is what makes the total time longer. Under Article 172, a less serious offence may be extended once (up to a further 2 months); a serious offence may be extended twice (a further 3 months, then 2 months); a very serious offence may be extended twice, each time up to 4 months; and a particularly serious offence may be extended up to three times, each time up to 4 months.
Added together, the maximum investigation period comes to about 4 months for a less serious offence, 8 months for a serious offence, 12 months for a very serious offence, and up to 16 months for a particularly serious offence. For a particularly serious and especially complex offence, the Chairman of the Supreme People's Procuracy may grant one further extension of up to 4 months, bringing it to nearly 20 months; for offences against national security it may be longer still. Cases with foreign elements are usually charged in the serious-and-above range (fraud, cross-border misappropriation of property, drugs, money laundering, and the like), so the real timeframe tends to sit in the upper half of this scale.
One notable change took effect in mid-2025: following the reorganisation of the procedural agencies under a new model, authority to extend an investigation now rests with the regional People's Procuracy and the provincial People's Procuracy (no longer the district level as before). The number of months in the investigation period itself remains unchanged; only the level of the authority empowered to grant extensions has changed.
Mutual legal assistance: why foreign elements slow a case down
If the investigation period does not distinguish by nationality, why do cases with foreign elements so often drag on? The key lies in the fact that many elements of the case are located outside Vietnamese territory, for example a statement, a bank account, a document or a witness abroad. To gather such evidence lawfully, the Vietnamese investigating authority must request mutual legal assistance from the foreign country.
The scope of assistance is broad: serving procedural documents, search and seizure, confiscating or returning assets, taking statements in person or online, transferring criminal prosecution, and exchanging information. The difficulty is that this process depends on the foreign side: it is carried out under an international treaty between the two countries, or on the principle of reciprocity, and must pass through many stages of verification, translation and approval on both sides. In practice, a request for mutual legal assistance can take many months, even more than a year, to produce results, and Vietnam cannot unilaterally shorten it.
This is also the "2026 update" the article wishes to emphasise: from 1 July 2026, the Law on Mutual Legal Assistance in Criminal Matters 2025 (Law No. 103/2025/QH15) officially takes effect, replacing the 2007 Law on Mutual Legal Assistance, which had combined civil matters, criminal matters and extradition. Assistance requests created or received before 1 July 2026 will still be handled under the old law; from that point on, mutual legal assistance in criminal matters, which sets the pace of cross-border cases, will operate under this new legal framework.
Suspension and resumption of the investigation: when the clock pauses
The natural next question is this: if the investigation period (even after extensions) expires while the results of mutual legal assistance from abroad have still not arrived, what then? Must the case be closed? The answer is no, and this is precisely why "how long" has no fixed number. In that situation, the investigating authority issues a decision to suspend the investigation.
In other words, when the time limit expires while the evidence from abroad has not arrived, the "clock" on the investigation period pauses, but the mutual legal assistance continues in the background until results are obtained. When the results arrive, the investigation is resumed and the authority is given a further period to complete it: under Article 174, the continued investigation period is no more than 2 months for less serious and serious offences, and no more than 3 months for very serious and particularly serious offences, and it too may be extended. It is precisely this "suspend then resume" cycle that allows a case with foreign elements, only a few months on paper, to last considerably longer in reality.
Detention for investigation: a separate term, not to be confused with the investigation period
For families with a loved one in custody, the greatest worry is not how long the case runs on paper, but how long their relative must remain in the detention centre. One important point must be grasped: the period of detention for investigation is a separate "clock", not the same as the investigation period, and it too is limited by law.
Detention may also be extended according to the seriousness of the offence, but the key point is this: once the detention period has expired and there is no basis to continue it, the detained person must be released or transferred to a lighter preventive measure. Detention is a preventive measure with a time limit, not a punishment, and still less a conclusion that a person is guilty. Under the principle of the presumption of innocence, a person is considered guilty only when there is a court conviction that has taken legal effect; before that point, even while in detention, they remain fully protected in their rights by law.
This is also why a case being suspended to await mutual legal assistance does not mean your loved one will be detained indefinitely: the detention period is calculated and controlled separately under Article 173, independently of the progress of the mutual legal assistance stage.
Common risks and mistakes in practice
The most common mistake is to expect a fixed "expiry date" on which the relative will be released. As analysed above, the investigation period may be extended several times, then suspended and resumed; while the detention period operates on an altogether different logic. Counting down to a single deadline almost always leads to disappointment and hasty decisions.
The second mistake is to misunderstand the procedural terms. "Suspension of investigation" is taken to mean the case has ended; "detention" is understood as "already guilty". These misconceptions cause families either to give up too early or to panic unnecessarily, when this is precisely the stage that calls for composure and action in the right direction.
The third mistake, and the most costly, is to wait until the case goes to trial before finding a lawyer. In reality, most of the statements and documents that shape the case file are laid down during the investigation and interrogation stage, especially when the person involved is a foreigner facing a language barrier and unfamiliar with Vietnamese procedure. A statement that is inaccurate because a question was misunderstood can follow the case all the way through. For families far away, a further serious risk lies in learning only that someone has "been arrested" and then losing contact entirely, with no idea where the relative is being held, how their health is, or what stage the case has reached, leading to the loss of crucial moments to protect their interests.
DEDICA's role when a loved one is caught up in a criminal case in Vietnam
In these situations, DEDICA accompanies the family from the very first difficult step: from the passport details and the initial information, our lawyers contact the competent authorities to determine where your loved one is being held in custody or detention, then register as defence counsel and take part in protecting them in the case. The lawyer attends the interrogation sessions to ensure that the client is not subjected to coercion or leading questioning and that all of their rights are observed, while also becoming a channel of information so that the family abroad can keep abreast of the situation, health and state of mind of the detained person.
Throughout the case, DEDICA closely follows the progress of the investigation, tracks when the case is suspended to await mutual legal assistance and when it is resumed, advises on defence strategy and, where there is a basis, assists with the procedure to change the preventive measure so as to obtain release on bail or guarantee. The aim is that the family need not guess in the dark, but always know where the case stands and what the next step should be.
Conclusion
So how long can the investigation in a case with foreign elements last? There is no single figure, but it can be pictured in four layers: (1) the basic investigation period, counted by offence category, with a maximum of about 4 months (less serious), 8 months (serious), 12 months (very serious) and 16 to nearly 20 months (particularly serious) after extensions; (2) if the time limit expires without results of mutual legal assistance from abroad, the case is suspended under Article 229, the "clock" pauses but the assistance continues; (3) when the results arrive, the investigation is resumed with a further period under Article 174; (4) in parallel, the detention period is calculated separately under Article 173, and once it expires without basis the person must be released or have the preventive measure changed. The date to remember for 2026: the Law on Mutual Legal Assistance in Criminal Matters No. 103/2025/QH15 takes effect on 1 July 2026 and largely governs whether a cross-border case moves slowly or quickly. Because the actual time depends heavily on the foreign side, what the family should do early is not to count down to a deadline, but to authorise a lawyer to locate the place of detention, register as defence counsel and closely follow the case's cycle of assistance and resumption.
Every criminal case with foreign elements differs in the offence charged, the procedural stage, and the country involved in the mutual legal assistance stage. If your loved one is involved in a case in Vietnam and you are abroad, DEDICA can help determine where they are being held, register as defence counsel and become a reliable channel of information for the family. Contact DEDICA for a lawyer to assess your specific situation and advise on the appropriate course of action.
This article is for reference only, based on the law in force at the time of writing. Each case depends on its specific file, evidence and procedural stage; please consult a DEDICA lawyer for accurate advice on your particular situation.
